Hydroperiod and salinity are known to determine species composition and ecosystem structure along the continuum of marsh to upland. Hydroperiod also influences biogeochemical processes some of which have the effect of producing toxic substances in soil under anaerobic conditions. Sulfides are toxic to vegetation and should be expected to be decreasing along the continuum toward the upland. Hydrology, marsh slope, and the effects of soil stressors are not well documented. By characterizing potential stressors (e.g., sulfides, salinity, hydroperiod, redox potential) along the marsh-upland continuum, we can begin to identify the relationship of slope and hydrology, and the effects on vegetation.